Ear mites are tenacious little boogers. You could bring them home to the cats (humans can be carriers for ear mites) from anywhere. They could also have something else, like an infection, but I'm willing to bet since they both have it, and it is only in the ears (right?) that its ear mites. It needs to be treated by a vet. DO NOT give any over-the-counter medications for ear mites, fleas, worms, etc to your cats. But a vet can clear it up with inexpensive, easy medications and a cleaning.
Vaccinations, well. If you do a search of this subforum, you will find several threads about just that-- indoor cats and vaccines. In most places a rabies vaccine is required by law, so you must get one. Other diseases are very easily spread, and you're better safe than sorry. And on top of that, bad things happen, such as an escape, a stray finding his way in, a disaster, etc. Some vaccines, on the other hand, you're probably better off without.
Zissou's Mom gave some very good reasons for having vaccinated cats. I was very glad that Willow had always been kept up to date on her vaccines when I brought Spot home at 2 am. Even though I kept him in a separate room and took him to the vet first thing in the morning, I found it reassuring that Willow had some protection against some of the possible things he could have brought home. The vaccines also help protect your cat when you take them to the vet. Vet offices are like people-doctor's offices--lots of sick beings hanging out in the waiting room.
If you are reluctant, you may want to ask your vet about alternating vaccine years or getting a titer test to see how strong your kitties' immunities are to each disease. That can help you decide whether you need to vaccinate them or not.
I get the rabies and 4 in 1 but not the leukeumia or FIV shots since my two are indoor only. The reason I get the 4 in 1 is because upper resp is very easily spread. Leukimia and FIV are not spread as easily. I get the rabies because it is required. and you never know, a bat could get in the house.